A process for the continuous production of low molecular weight, di-terminated polyphenylene ether capped with an unsaturated group

Abstract

The application belongs to the technical field of continuous synthesis of new polymer materials, and discloses a method for continuously producing low-molecular-weight double-end-group polyphenyl ether terminated by unsaturated groups. The method uses a continuous micro-channel reaction process to prepare low-molecular-weight double-end-group polyphenyl ether terminated by unsaturated groups, eliminates a large-capacity reaction kettle for high-speed stirring in the oxidation reaction process, adjusts the pH value and impurity content of the reaction system by using CO2 and NH3 gas in stages to meet the active catalytic conditions required by catalysts in different reaction stages, reduces by-products and catalyst residues, cancels the washing, dissolution, purification, precipitation and drying process operations required for intermediate products in the batch production of reaction kettles, and improves the safety risk and production efficiency of the process technology.

Description

Technical Field

[0001] This invention belongs to the field of continuous synthesis technology of novel polymer materials, and specifically relates to a method for the continuous production of low molecular weight double-terminated polyphenylene ethers with unsaturated group-capped ends. Background Technology

[0002] Currently, there are two main technical routes for the synthesis of low molecular weight polyphenylene ethers (PPOs) with dual-terminal groups: The first route involves first preparing tetramethylbisphenol A (TPA) and similar small-molecule phenolic derivatives. Then, high-molecular-weight PPO is redistributed or depolymerized with the phenolic derivatives under the action of an initiator to obtain low-molecular-weight PPOs with dual-terminal hydroxyl groups. Finally, the low-molecular-weight PPOs with dual-terminal hydroxyl groups undergo alcoholysis with acid anhydrides under heating conditions. The characteristics of this route are: 1. Mature process and technology; 2. Wide molecular weight distribution of the product; 3. Incomplete reaction of high-molecular-weight PPO; 4. Low content of terminal functionalized groups.

[0003] The second technical route differs from the first in the process for preparing low-molecular-weight terminal hydroxyl polyphenylene ether products. It directly utilizes the oxidative coupling reaction between 2,6-dimethylphenol and a diphenol in a metal complex catalyzed manner. The advantages of this route are a high content of terminal functionalized groups and a uniform molecular weight distribution. However, this reaction involves redox reactions, resulting in a high risk factor, complex process, numerous byproducts, and high technical requirements.

[0004] Chinese invention patents CN201510181415.8 (granted) and CN202210328468.8 (published) both disclose the first technical route, which prepares low-molecular-weight thermosetting polyphenylene ether by cutting and rearranging high-molecular-weight polyphenylene ether. Chinese invention patent CN201910230050.1 discloses a method for manufacturing high intrinsic viscosity polyphenylene ether, using three reactors connected in series to prepare single-ended high-molecular-weight polyphenylene ether. Chinese invention patent CN202210286381.9 discloses a preparation system and method for dihydroxy polyphenylene ether, employing the second technical route using 2,6-dimethylphenol and tetramethylbisphenol A as raw materials, and using two reactors connected in series to prepare dihydroxy-terminated low-molecular-weight polyphenylene ether. Chinese invention patent CN201911213241.3 discloses a polyphenylene ether intermediate, a polyphenylene ether derivative, a preparation method thereof, and an application thereof. The invention uses a batch reactor to prepare phenolic derivatives and polyphenylene ether products containing cycloalkyl or asymmetric branched alkyl groups.

[0005] Both technical routes share a common feature: they require the initial preparation of two intermediate products, tetramethylbisphenol A and low-molecular-weight dihydroxyl-terminated polyphenylene ether. Since the catalytic system used for each intermediate product has different requirements regarding pH value, impurity components, and their concentrations, each intermediate product requires stirring and reaction in different reactors, followed by complex washing, dissolving, purification, precipitation, and drying processes. The preparation process involves numerous steps, complex operations, long production cycles, and poor product quality stability. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a system for the continuous production of low molecular weight bi-terminated polyphenylene ethers with unsaturated groups at the end.

[0007] Another objective of this invention is to provide a continuous production method for low molecular weight di-terminated polyphenylene ethers (PPEs) with unsaturated group-terminated capping. This method employs a continuous microchannel reaction process to prepare PPEs with unsaturated group-terminated capping, eliminating the need for large-capacity reactors with high-speed stirring during oxidation reactions. By using CO2 and NH3 gases to adjust the pH and impurity content of the reaction system in stages, the active catalytic conditions required by the catalyst at different reaction stages are met, reducing byproducts and catalyst residues. It also eliminates the washing, dissolving, purification, precipitation, and drying processes required for intermediate products in batch reactor production, thereby improving process safety and production efficiency.

[0008] The objective of this invention is achieved through the following solution:

[0009] A system for the continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated ends includes pipeline 1, pipeline 2, pipeline 3, and a vacuum drying device. The three pipelines share a single microchannel reactor. Pipeline 1 includes a gas tank (1), a gas switching valve (A-1), a microchannel reactor (3), a regulating switch 1 (A-3), a fluidized bed (4), a gas-liquid separator 1 (5), and a detector 1 (6). The outlet of the gas tank (1) is connected to the inlet of the gas switching valve (A-1), and the outlet of the gas switching valve (A-1) is connected to the microchannel reactor. The inlet of the channel reactor (3) is connected to the outlet of the microchannel reactor (3), which is connected to the inlet of the regulating switch 1 (A-3). The outlet of the regulating switch 1 (A-3) is connected to the inlet of the fluidized bed (4), which is connected to the inlet of the gas-liquid separator 1 (5). The outlet of the gas-liquid separator 1 (5) is connected to the inlet of the detector 1 (6), which is connected to the inlet of the microchannel reactor (3). The gas tank (1) includes an O2 gas tank, a CO2 gas tank, and an NH3 gas tank.

[0010] The pipeline 2 includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), a regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), and a regulating switch 2 (A-4); the outlet of the raw material tank (2) is connected to the inlet of the raw material switching valve (A-2), the outlet of the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), the outlet of the regulating switch 1 (A-3) is connected to the inlet of the gas-liquid separator 2 (7), the outlet of the gas-liquid separator 2 (7) is connected to the inlet of the detector 2 (8), the outlet of the detector 2 (8) is connected to the inlet of the regulating switch 2 (A-4), and the outlet of the regulating switch 2 (A-4) is connected to the inlet of the microchannel reactor (3); wherein the raw material tank (2) includes raw material tank 1, raw material tank 2, raw material tank 3, and raw material tank 4;

[0011] The pipeline 3 consists of pipeline 2, liquid-liquid centrifuge (9), detector 3 (10), and regulating switch 3 (A-5). Specifically, it includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), regulating switch 2 (A-4), liquid-liquid centrifuge (9), detector 3 (10), and regulating switch 3 (A-5). The outlet of the raw material tank (2) is connected to the inlet of the raw material switching valve (A-2), the outlet of the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), and the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3). The outlet of A-3) is connected to the inlet of gas-liquid separator 2 (7), the outlet of gas-liquid separator 2 (7) is connected to the inlet of detector 2 (8), the outlet of detector 2 (8) is connected to the inlet of liquid-liquid centrifuge (9) through adjustment switch 2 (A-4), the outlet of liquid-liquid centrifuge (9) is connected to the inlet of detector 3 (10), the outlet of detector 3 (10) is connected to the inlet of adjustment switch 3 (A-5), the outlet of adjustment switch 3 (A-5) is connected to the first half of pipeline 2 so that the reaction liquid can return to the microchannel reactor for reaction. At the same time, adjustment switch 3 (A-5) is connected to vacuum drying equipment (11) so that when the online detector 3 (10) detects that it is qualified, the reaction liquid is released for vacuum drying.

[0012] A method for the continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated ends includes the following steps:

[0013] S1. Using pipeline 1, CO2 gas is added to the pipeline through gas switching valve (A-1). At the same time, 2,6-dimethylphenol and xylene mixed solution (raw material tank 1) and ketone compounds (raw material tank 2) are added through raw material switching valve (A-2) in pipeline 2. After being fully mixed in the microchannel reactor (3), the mixture enters the fluidized bed (4) loaded with catalyst in pipeline 1 for reaction. The reaction liquid enters the detector 1 (6) for online detection after passing through gas-liquid separator 1 (5) in pipeline 1. Then the reaction liquid continues to return to the microchannel reactor, and CO2 gas is continuously introduced. The reaction liquid circulates in pipeline 1 until the detection is qualified. Then the carbon dioxide gas is turned off, and the reaction liquid enters pipeline 2 through the adjustment switching switch 1 (A-3) in pipeline 2.

[0014] S2. After the reaction liquid enters the pipeline 2, NH3 and O2 gas are added to the pipeline through the gas switching valve (A-1) in the pipeline 1. The flow rates of NH3 and O2 are adjusted. The catalyst CuCl2 solution (raw material tank 3) is added through the raw material switching valve (A-2). The reaction liquid reacts rapidly in the microchannel reactor (3). After passing through the gas-liquid separator 2 (7), it is detected online by the detector 2 (8). NH3 and O2 are continuously introduced. The reaction liquid circulates in the pipeline 2 until the detection is qualified. The switching switch 2 (A-4) is adjusted to allow the reaction liquid to enter the pipeline 3.

[0015] S3. First, use the liquid-liquid centrifuge (9) in pipeline 3 to separate the by-product water generated in step S2, and then use the conversion switch 3 (A-5) to return the reaction liquid to pipeline 2 for circulation; add the mixture of unsaturated acid anhydride and catalyst (raw material tank 4) through the raw material conversion valve (A-2), adjust the CO2 gas pressure, and make the mixture and the reaction liquid in the pipeline quickly mix / react in the microchannel reactor (3). After passing through the gas-liquid separator 2 (7), it is detected online. The reaction liquid circulates in pipeline 2, and the acid anhydride residue and polyphenylene ether product hydroxyl residue are detected online through the detector 2 (8) until the detection is qualified; after the reaction liquid is qualified, it is transferred through the gas conversion valve (A-5) in pipeline 1. 1) A certain amount of NH3 gas is introduced into the reaction system, and a certain amount of pure water is added through the raw material switching valve (A-2) in pipeline 2. When the impurities in the reaction solution pass through the microchannel reactor (3), they are fully mixed / extracted and dissolved in the aqueous phase. Adjust the switching switch (A-4) in pipeline 2, and the reaction solution enters the liquid-liquid centrifuge device (9) for centrifugation and phase separation to obtain the organic phase containing the product. The product is then tested online by the detector 3 (10). If the test fails, NH3 gas and the same amount of water are introduced again for repeated mixing / extraction until the residual amount is qualified. The solvent is removed by the vacuum drying device (11) to obtain the low molecular weight double-terminated polyphenylene ether product with unsaturated group end caps.

[0016] In step S1, the mass ratio of 2,6-dimethylphenol to xylene in the raw material tank 1 is 1:1 to 1:2, preferably 1:1.75, and the temperature of the raw material tank 1 is maintained at 45 to 70°C.

[0017] In step S1, the ketone compound is a straight-chain or cyclic aliphatic ketone compound, preferably acetone, and the mass ratio of the ketone compound to 2,6-dimethylphenol entering the reaction tube is 1:20 to 1:30, preferably 1:25.

[0018] In step S1, by adjusting the flow rate of CO2 gas, the inlet pressure of the microchannel reactor is maintained at 0.15-0.45 MPa, so that the reaction liquid is fully mixed when passing through the microchannel reactor (3), replacing the traditional stirring device, and at the same time maintaining the pH value of the system at 6.0±0.2, in conjunction with the acidic catalyst in the fluidized bed.

[0019] In step S1, the microchannel reactor (3) is composed of commercially available strip / star modular microchannel reactors connected in series. An air inlet is connected between the series pipelines to ensure a strong mixing and collision effect between the gas and the reaction liquid. The temperature of the microchannel reactor is controlled at 55-60℃, and the single-pass residence time of the reaction liquid in the microchannel is 3-8 min.

[0020] In step S1, the catalyst of the fluidized bed (4) is polyphosphoric acid supported on diatomaceous earth, and the reaction temperature of the fluidized bed is controlled at 55-60°C.

[0021] In step S1, the qualified test means that the residual ketone compound and the product yield are monitored online in detector 1 (6). The judgment index is: the conversion rate of raw material ketone compound > 99% and the yield of target product (tetramethylbisphenol A) > 97%.

[0022] In step S2, the flow rate of NH3 is adjusted to maintain the pH value of the system between 7.5 and 8.5, and the O2 inlet flow rate is adjusted to maintain the inlet pressure of the microchannel reactor at 0.25 to 0.65 MPa. The total oxygen inlet flow rate and the molar ratio of 2,6-dimethylphenol in the reaction pipeline system during the reaction process are 1.2 to 1.7:1.

[0023] In step S2, the temperature of the microchannel reactor (3) is controlled at 35-55°C by an external temperature control system. The single-pass residence time of the reaction liquid in the microchannel reactor is 1.5-5 min, and the total reaction residence time in the microchannel is 1.5-30 min.

[0024] In step S2, the CuCl2 solution is preferably a saturated CuCl2 solution, and the catalyst CuCl2 accounts for 0.05 to 0.2% of the mass fraction of 2,6-dimethylphenol in the initial reaction pipeline system;

[0025] In step S2, the residues of 2,6-dimethylphenol, bisphenol A residues, by-product content, product molecular weight, and molecular weight distribution width index of the raw material are monitored online by detector 2 (8). The qualified detection criteria are: 2,6-dimethylphenol conversion rate > 99.5% and molecular weight distribution width 1.50 to 1.55. Reference index parameters (not used for judgment): bisphenol A residue < 2%, by-product content < 0.8%, and product molecular weight 750 to 3500.

[0026] In step S3, after the reaction solution is centrifuged, the residual water content in the reaction solution is controlled to be no more than 0.15% to prevent hydrolysis of acid anhydride and reduce utilization rate.

[0027] In step S3, the unsaturated anhydride can be an aliphatic or aromatic unsaturated anhydride, preferably methacrylic anhydride, and the amount of unsaturated anhydride added is 10% to 20% of the mass fraction of 2,6-dimethylphenol in the initial reaction system; the catalyst is a hybrid compound containing lone pairs of electrons, preferably N,N-dimethylaminopyridine, and the amount added is 1% to 5% of the mass fraction of 2,6-dimethylphenol in the initial reaction system;

[0028] In step S3, the CO2 inlet pressure is adjusted to maintain the inlet pressure of the microchannel reactor at 0.2-0.5 MPa, so that the acid anhydride mixture and the reaction liquid in the pipeline are fully mixed / collided, thereby accelerating the reaction rate.

[0029] In step S3, when adding the mixture of unsaturated anhydride and catalyst, the temperature of the microchannel reactor is controlled to be 80-110℃, the single-pass time through the microchannel reactor is 2-8 min, and the total reaction residence time in the microchannel is 30-60 min.

[0030] In step S3, the residual acid anhydride in the raw material and the residual hydroxyl group in the polyphenylene ether product are detected online by detector 2 (8) until the detection is qualified. The judgment index for qualified detection is: residual phenolic hydroxyl group in polyphenylene ether product <300ppm;

[0031] In step S3, NH3 gas is introduced to neutralize the residual anhydride and the acid produced in the reaction, and the pH value of the reaction system is controlled at 7.0±0.2. Then, the introduction of NH3 is stopped. Pure water is added, and the mass ratio of pure water to 2,6-dimethylphenol in the initial reaction system is 0.5 to 1.2:1.

[0032] In step S3, the online inspection of detector 3 (10) is qualified, which means that the online monitoring of catalyst, metal ion and inorganic salt ion residues is qualified. The judgment index is: catalyst residue < 5000 ppm, metal (copper) ion residue < 200 ppm, chloride ion residue < 100 ppm, methacrylic acid and acid anhydride total ions < 300 ppm.

[0033] In step S3, the number average molecular weight of the low molecular weight dual-terminated polyphenylene ether product is in the range of 750 to 3500.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] (1) By repeatedly utilizing the different acidity and alkalinity of CO2 and NH3 gases at different reaction stages, the pH value of the reaction system is controlled, eliminating the influence of different solvent environments on catalyst activity. This eliminates the need for washing, dissolving, purifying, precipitating, and drying intermediate products in batch reactor production, thereby improving production efficiency. The reaction time of bisphenol A products in S1 is shortened from 24–48 h to 1–4 h, the reaction time of terminal hydroxyl low molecular weight polyphenylene ether products in S2 is shortened from 12–18 h to 5–30 min, and the reaction time of products in S3 is shortened from 18–24 h to 0.5–1.5 h. The entire synthesis and purification process time is shortened from 7–10 days to 8–16 h.

[0036] (2) CO2 and NH3, while adjusting the pH value, change the types and contents of by-products. CO2 is used to replace the strong liquid acid in the synthesis of bisphenol A, and NH3 is used to replace the organic amine in the synthesis of terminal hydroxyl polyphenylene ether as a catalyst. This avoids the organic amine from entering the main chain of the product molecule, neutralizes the organic acid produced in the third stage reaction, dissolves the interaction between residual CO2 and NH3, eliminates the trace amount of catalyst residue in the final product, improves the dielectric properties of the material, and is beneficial to the application of the product in the high frequency and high speed circuit board industry where high dielectric properties are required.

[0037] (3) It can effectively control the temperature change of the system caused by the exothermic reaction, with few by-product reactions, a narrow molecular weight distribution of the product (1.50-1.55), light sample color, yellowness index of 1% toluene solution (150-350), and yield >90%.

[0038] (4) By using a gas flow rate and a microchannel mixer, high-speed / full mixing of materials can be achieved. The three batch reaction devices in the polyphenylene ether synthesis process can be replaced by a continuous reaction process, making the reaction process more stable and efficient, and reducing safety risks. The catalysis of each reaction stage needs to exhibit catalytic activity under specific conditions. By utilizing the different acidity and alkalinity of CO2 and NH3 gases, the pH value of each reaction stage is strictly controlled so that the catalytic system of the subsequent reaction still has catalytic activity in the reaction solution of the previous step, and the solvent can be continuously utilized. In the reaction, CO2 or NH3 needs to be continuously used to react with the by-products or residual raw materials generated in the previous stage reaction, and then the good water solubility of the product is used for separation. The gas pressure and flow rate of each stage need to be controlled to achieve good mixing and reaction effect, thereby reducing the washing / purification and drying steps of intermediate products. Attached Figure Description

[0039] Figure 1 This invention relates to a system for the continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping, comprising: 1-gas tank, 2-raw material tank, 3-microchannel reactor, 4-fluidized reaction bed, 5-gas-liquid separator 1, 6-detector 1, 7-gas-liquid separator, 8-detector 2, 9-liquid-liquid centrifuge, 10-detector 3, 11-vacuum drying equipment; A-1 is a gas switching valve, A-2 is a raw material switching valve, A-3 is a regulating switching switch, A-4 is a regulating switching switch, and A-5 is a regulating switching switch.

[0040] Figure 2 The mass spectrum of the intermediate product tetramethyldimethyl A;

[0041] Figure 3 The molecular weight distribution of the intermediate product, terminal hydroxyl low molecular weight polyphenylene ether. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0043] The system for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping in this invention is as follows: Figure 1 As shown, it includes pipeline 1, pipeline 2, pipeline 3 and vacuum drying equipment; among them, the regulating switch (A-3, A-4, A-5) is a three-way switching structure with one inlet and two different outlets. By switching, it can connect to pipeline 1 or the other two pipelines respectively.

[0044] The pipeline 1 includes a gas tank (1), a gas switching valve (A-1), a microchannel reactor (3), a regulating switch 1 (A-3), a fluidized bed (4), a gas-liquid separator 1 (5), and a detector 1 (6); the outlet of the gas tank (1) is connected to the gas switching valve (A-1), the gas switching valve (A-1) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), the outlet of the regulating switch 1 (A-3) is connected to the inlet of the fluidized bed (4), the outlet of the fluidized bed (4) is connected to the inlet of the gas-liquid separator 1 (5), the outlet of the gas-liquid separator 1 (5) is connected to the detector 1 (6), and the detector 1 (6) is connected to the inlet of the microchannel reactor (3); wherein the gas tank (1) includes an O2 gas tank, a CO2 gas tank, and an NH3 gas tank;

[0045] The pipeline 2 includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), a regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), and a regulating switch 2 (A-4); the outlet of the raw material tank (2) is connected to the raw material switching valve (A-2), the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the regulating switch 1 (A-3), the outlet of the regulating switch 1 (A-3) is connected to the inlet of the gas-liquid separator 2 (7), the outlet of the gas-liquid separator 2 (7) is connected to the inlet of the detector 2 (8), the outlet of the detector 2 (8) is connected to the inlet of the regulating switch 2 (A-4), and the outlet of the regulating switch 2 (A-4) is connected to the inlet of the microchannel reactor (3); wherein the raw material tank (2) includes raw material tank 1, raw material tank 2, raw material tank 3, and raw material tank 4;

[0046] The pipeline 3 consists of pipeline 2, liquid-liquid centrifuge (9), detector 3 (10), and regulating switch 3 (A-5). Specifically, it includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), regulating switch 2 (A-4), liquid-liquid centrifuge (9), detector 3 (10), and regulating switch 3 (A-5). The outlet of the raw material tank (2) is connected to the inlet of the raw material switching valve (A-2), the outlet of the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), and the outlet of the regulating switch 1 (A-3) is connected to... The inlet of gas-liquid separator 2 (7) is connected, the outlet of gas-liquid separator 2 (7) is connected to the inlet of detector 2 (8), the outlet of detector 2 (8) is connected to the inlet of liquid-liquid centrifuge (9) through adjustment switch 2 (A-4), the outlet of liquid-liquid centrifuge (9) is connected to the inlet of detector 3 (10), the outlet of detector 3 (10) is connected to the inlet of adjustment switch 3 (A-5), adjustment switch 3 (A-5) is connected to the first half of pipeline 2 so that the reaction liquid can return to the microchannel reactor for reaction, and at the same time connected to vacuum drying equipment (11) so that the reaction liquid can be released for vacuum drying when the online detector 3 (10) detects that it is qualified; wherein the raw material tank (2) includes raw material tank 1, raw material tank 2, raw material tank 3 and raw material tank 4)

[0047] Example 1

[0048] Adjust the CO2 gas inlet pressure to 0.3 MPa, and introduce CO2 gas into the pipeline through the gas switching valve (A-1). At the same time, add 8250g of a mixed solution of 2,6-dimethylphenol and xylene (raw material tank 1) (2,6-dimethylphenol to xylene mass ratio 1:1.75, 8250g contains 3000g of 2,6-dimethylphenol and 5250g of xylene), and then add 120g of acetone (raw material tank 2) into the pipeline. The pH of the system was adjusted to 6.1, and the temperature of the microchannel reactor was controlled at 55°C. After the reaction solution was fully mixed and preheated in the microchannel reactor (3), it entered the fluidized bed (4) loaded with catalyst for reaction. The temperature of the solid bed fluidized bed was set to 60°C. After the reaction solution passed through the gas-liquid separator 1 (5), it entered the detector 1 (6) for online detection. Subsequently, the reaction solution continued to return to the microchannel reactor, and CO2 gas was continuously introduced. The reaction solution circulated in pipeline 1 until the detection was qualified. The result of the reaction termination judgment was: acetone conversion rate 99.2%, and intermediate product tetramethylbisphenol A yield 97.8%. The carbon dioxide gas was turned off, and the conversion switch 1 (A-3) was adjusted to allow the reaction solution to enter pipeline 2. The mass spectrometry data of the intermediate product tetramethylbisphenol A are as follows. Figure 2 As shown.

[0049] NH3 was added to pipe 2 to maintain the pH of the system at 7.5, and a certain amount of O2 was introduced at the same time. The oxygen inlet pressure of the microchannel reactor was 0.5 MPa. A catalyst solution containing 3.0 g of CuCl2 was added through the raw material switching valve (A-2). The temperature of the microchannel reactor (3) was controlled at 50 ± 2 °C. The reaction solution reacted rapidly in the microchannel reactor. After passing through the gas-liquid separator 2 (7), it was detected online by the detector 2 (8). NH3 and O2 were continuously introduced. The reaction solution circulated in pipe 2 until the detection was qualified. The entire reaction lasted for 15 min. 900 L of oxygen was introduced during the 15 min of the reaction. Samples were continuously taken during the reaction for monitoring. The results of the reaction are shown in Table 1. The molecular weight and distribution test results of the intermediate products are shown in Table 1. Figure 3 As shown.

[0050] Table 1. Process monitoring data for the synthesis of intermediate product terminal hydroxyl low molecular weight polyphenylene ether.

[0051]

[0052] Adjust the switching switch 2 (A-4) to allow the reaction liquid to enter the liquid-liquid centrifuge (9) in pipeline 3, separating the byproduct water generated in step S2, so that the water content in the reaction liquid is 0.09%. Then, adjust the switching switch 3 (A-5) to allow the reaction liquid to return to pipeline 2 for circulation. Add 450g of methacrylic anhydride and 60g of catalyst N,N-dimethylaminopyridine (raw material tank 4) through the raw material switching valve (A-2), adjust the CO2 gas inlet pressure to 0.4Mpa, and control the microchannel reactor temperature to 105℃, so that the mixture and the reaction liquid in the pipeline are rapidly mixed / reacted in the microchannel reactor (3). After passing through the gas-liquid separator 2 (7), the reaction liquid is detected online. The reaction liquid circulates in pipeline 2 until the residual phenolic hydroxyl value of the polyphenylene ether product is 280ppm, at which point the reaction is stopped.

[0053] A certain amount of NH3 gas is introduced into the reaction system through the gas switching valve (A-1) to control the pH value of the reaction system to 7.0±0.2. At the same time, 3000g of pure water is added through the raw material switching valve (A-2). Impurities in the reaction solution are fully mixed / extracted and dissolved in the aqueous phase when passing through the microchannel reactor. The liquid-liquid centrifuge (9) connected to pipeline 3 is used for centrifugation and phase separation to obtain the organic phase containing the product. The residual amount is detected online. After repeated mixing / extraction with water, a reaction solution with 3800ppm of catalyst residue and 76ppm of metal ion residue is obtained. The solvent is removed by vacuum drying equipment (11) to obtain a low molecular weight double-terminated polyphenylene ether product with unsaturated group-terminated ends.

[0054] The experiment was conducted with reference to Example 1, and Examples 2 to 4 and Comparative Examples 1 to 2 were carried out in sequence. The experimental conditions for each example and comparative example are shown in Table 2.

[0055] Table 2. Summary of experimental conditions for the examples and comparative examples

[0056]

[0057] The performance of the unsaturated group-capped low molecular weight double-ended polyphenylene ether products obtained in each embodiment and comparative example was tested, and the test results are shown in Table 3.

[0058] Table 3. Performance of low molecular weight di-terminated polyphenylene ethers with various unsaturated groups in the Examples and Comparative Examples

[0059]

[0060] The unsaturated group-terminated low molecular weight double-ended polyphenylene ether products obtained from the various examples and comparative examples were used to press circuit board products. The performance of the pressed samples was tested, and the test results are shown in Table 4.

[0061] Table 4. Performance of the pressed circuit board prototypes prepared according to each embodiment and comparative example

[0062]

[0063] The performance comparison shows that, in the examples, by adjusting the raw material ratio and the air mixing parameters at each stage, the molecular weight of the product can vary within a certain range, but the molecular weight distribution of the product is narrow, the content of the two ends remains above 90%, and the yield can reach 90%, exhibiting good product yield, low phenolic hydroxyl residue, low by-product content, and low color. When the pH value, air pressure, or reaction time changes significantly during the reaction stage, the by-products increase in the comparative example, the content of the two ends of the product is low, ultimately affecting the high-temperature resistance and dielectric loss performance during application.

[0064] As can be seen from the examples, the reaction time from raw materials to products can be shortened to 3-5 hours. Including centrifugation and drying time, the entire synthesis and purification process can be controlled to 8-16 hours, which is significantly shorter than the 7-10 days required by the current three-stage batch production method, and the production efficiency is significantly improved.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A system for the continuous production of low molecular weight, double-terminated polyphenylene ethers with unsaturated groups capped, characterized in that... The system includes pipeline 1, pipeline 2, pipeline 3, and vacuum drying equipment. Pipeline 1 includes a gas tank (1), a gas switching valve (A-1), a microchannel reactor (3), a regulating switch 1 (A-3), a fluidized bed (4), a gas-liquid separator 1 (5), and a detector 1 (6). The outlet of the gas tank (1) is connected to the inlet of the gas switching valve (A-1), the outlet of the gas switching valve (A-1) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), the outlet of the regulating switch 1 (A-3) is connected to the inlet of the fluidized bed (4), the outlet of the fluidized bed (4) is connected to the inlet of the gas-liquid separator 1 (5), the outlet of the gas-liquid separator 1 (5) is connected to the inlet of the detector 1 (6), and the outlet of the detector 1 (6) is connected to the inlet of the microchannel reactor (3). The gas tank (1) includes an O2 gas tank, a CO2 gas tank, and an NH3 gas tank. The pipeline 2 includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), a regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), and a regulating switch 2 (A-4); the outlet of the raw material tank (2) is connected to the inlet of the raw material switching valve (A-2), the outlet of the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), the outlet of the regulating switch 1 (A-3) is connected to the inlet of the gas-liquid separator 2 (7), the outlet of the gas-liquid separator 2 (7) is connected to the inlet of the detector 2 (8), the outlet of the detector 2 (8) is connected to the inlet of the regulating switch 2 (A-4), and the outlet of the regulating switch 2 (A-4) is connected to the inlet of the microchannel reactor (3); wherein the raw material tank (2) includes raw material tank 1, raw material tank 2, raw material tank 3, and raw material tank 4; The pipeline 3 includes a raw material tank (2), a raw material switching valve (A-2), a microchannel reactor (3), a regulating switch 1 (A-3), a gas-liquid separator 2 (7), a detector 2 (8), a regulating switch 2 (A-4), a liquid-liquid centrifuge (9), a detector 3 (10), and a regulating switch 3 (A-5); the outlet of the raw material tank (2) is connected to the inlet of the raw material switching valve (A-2), the outlet of the raw material switching valve (A-2) is connected to the inlet of the microchannel reactor (3), the outlet of the microchannel reactor (3) is connected to the inlet of the regulating switch 1 (A-3), and the outlet of the regulating switch 1 (A-3) is connected to the inlet of the gas-liquid separator 2 (7). The outlet of the gas-liquid separator 2 (7) is connected to the inlet of the detector 2 (8). The outlet of the detector 2 (8) is connected to the inlet of the liquid-liquid centrifuge (9) through the adjustment switch 2 (A-4). The outlet of the liquid-liquid centrifuge (9) is connected to the inlet of the detector 3 (10). The outlet of the detector 3 (10) is connected to the inlet of the adjustment switch 3 (A-5). The outlet of the adjustment switch 3 (A-5) is connected to the first half of the pipeline 2 so that the reaction liquid can return to the microchannel reactor for reaction. At the same time, the adjustment switch 3 (A-5) is connected to the vacuum drying equipment (11) so that the reaction liquid can be released for vacuum drying when the online detector 3 (10) detects that it is qualified.

2. A method for continuous production of unsaturated group-terminated low molecular weight double-ended polyphenylene ether using the continuous production system as described in claim 1, characterized in that, Includes the following steps: S1. Using pipeline 1, CO2 gas is added to the pipeline through gas switching valve (A-1). At the same time, 2,6-dimethylphenol and xylene mixed solution in raw material tank 1 and ketone compounds in raw material tank 2 are added through raw material switching valve (A-2) in pipeline 2. After being fully mixed in microchannel reactor (3), the mixture enters the fluidized bed (4) loaded with catalyst in pipeline 1 for reaction. The reaction liquid enters detector 1 (6) for online detection after passing through gas-liquid separator 1 (5) in pipeline 1. Then the reaction liquid continues to return to microchannel reactor, and CO2 gas is continuously introduced. The reaction liquid circulates in pipeline 1 until the detection is qualified. Then the carbon dioxide gas is turned off, and the reaction liquid enters pipeline 2 through adjustment switching switch 1 (A-3) in pipeline 2. S2. After the reaction liquid enters the pipeline 2, NH3 and O2 gas are added to the pipeline through the gas switching valve (A-1) in the pipeline 1. The flow rates of NH3 and O2 are adjusted. The catalyst CuCl2 solution in the raw material tank is added through the raw material switching valve (A-2). The reaction liquid reacts rapidly in the microchannel reactor. After passing through the gas-liquid separator 2 (7), it is detected online by the detector 2 (8). NH3 and O2 are continuously introduced. The reaction liquid circulates in the pipeline 2 until the detection is qualified. The switching switch 2 (A-4) is adjusted to allow the reaction liquid to enter the pipeline 3. S3. First, use the liquid-liquid centrifuge device (9) in pipeline 3 to separate the by-product water generated in step S2. Then, adjust the conversion switch 3 (A-5) to make the reaction liquid return to pipeline 2 for circulation. Add the mixture of unsaturated acid anhydride and catalyst in raw material tank 4 through the raw material conversion valve (A-2), adjust the CO2 gas pressure, and make the mixture and the reaction liquid in the pipeline quickly mix and react in the microchannel reactor (3). After passing through the gas-liquid separator 2 (7), it is detected online. The reaction liquid circulates in pipeline 2. The acid anhydride residue and polyphenylene ether product hydroxyl residue are detected online through the detector 2 (8) until the test is qualified. After the reaction solution passes the test, NH3 gas is introduced into the reaction system through the gas switching valve (A-1) in pipeline 1, and pure water is added through the raw material switching valve (A-2) in pipeline 2. When the impurities in the reaction solution pass through the microchannel reactor (3), they are fully mixed and extracted and dissolved in the aqueous phase. The switching switch 2 (A-4) in pipeline 2 is adjusted, and the reaction solution enters the liquid-liquid centrifuge (9) for centrifugation and phase separation to obtain the organic phase containing the product. The product passes the online test by the detector 3 (10). The solvent is removed by the vacuum drying equipment (11) to obtain the low molecular weight double-terminated polyphenylene ether product with unsaturated group end caps.

3. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S1, the mass ratio of 2,6-dimethylphenol to xylene in raw material tank 1 is 1:1 to 1:2, and the temperature of raw material tank 1 is maintained at 45 to 70°C. In step S1, the ketone compound is a straight-chain or cyclic aliphatic ketone compound, and the mass ratio of the ketone compound to 2,6-dimethylphenol in the reaction tube is 1:20 to 1:

30. In step S1, the inlet pressure of the microchannel reactor is maintained at 0.15 to 0.45 MPa by adjusting the flow rate of CO2 gas, while the pH value of the system is maintained at 6.0 ± 0.

2.

4. The method for continuous production of low molecular weight double-terminated polyphenylene ethers with unsaturated group-capped ends according to claim 3, characterized in that: In step S1, the mass ratio of 2,6-dimethylphenol to xylene in the raw material tank 1 is 1:1.75; In step S1, the ketone compound is acetone, and the mass ratio of the ketone compound to 2,6-dimethylphenol entering the reaction tube is 1:

25.

5. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S1, the microchannel reactor (3) is composed of commercially available strip / star modular microchannel reactors connected in series. The temperature of the microchannel reactor is controlled at 55-60℃, and the residence time of the reaction liquid in the microchannel is 3-8 min. In step S1, the catalyst of the fluidized bed (4) is polyphosphoric acid supported on diatomaceous earth, and the reaction temperature of the fluidized bed is controlled at 55-60°C. In step S1, the qualified test means that the residual ketone compound and the product yield are monitored online in detector 1 (6). The judgment index is: the conversion rate of raw material ketone compound > 99% and the yield of target product tetramethylbisphenol A > 97%.

6. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S2, the flow rate of NH3 is adjusted to maintain the pH value of the system between 7.5 and 8.5, and the O2 inlet flow rate is adjusted to maintain the inlet pressure of the microchannel reactor at 0.25 to 0.65 MPa. The total oxygen inlet flow rate and the molar ratio of 2,6-dimethylphenol in the reaction pipeline system during the reaction process are 1.2 to 1.

7. In step S2, the temperature of the microchannel reactor (3) is controlled at 35-55°C by an external temperature control system. The single-pass residence time of the reaction liquid in the microchannel reactor is 1.5-5 min, and the total reaction residence time in the microchannel is 1.5-30 min.

7. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S2, the CuCl2 solution is a saturated CuCl2 solution, and CuCl2 accounts for 0.05 to 0.2% of 2,6-dimethylphenol in the initial reaction pipeline system, by mass fraction; In step S2, the qualified test criteria are that the conversion rate of the raw material 2,6-dimethylphenol is >99.5% and the molecular weight distribution width is 1.50 to 1.

55.

8. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S3, after the reaction solution is centrifuged, the residual water content in the reaction solution is controlled to be ≤0.15%. In step S3, the unsaturated anhydride is an aliphatic or aromatic unsaturated anhydride, and the amount of unsaturated anhydride added is 10% to 20% of 2,6-dimethylphenol in the initial reaction system, by mass fraction; the catalyst is a hybrid compound containing lone pairs of electrons, and the amount added is 1% to 5% of 2,6-dimethylphenol in the initial reaction system, by mass fraction.

9. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 8, characterized in that: In step S3, the unsaturated acid anhydride is methacrylic anhydride; The catalyst is N,N-dimethylaminopyridine.

10. A method for continuous production of low molecular weight bipolar polyphenylene ethers capped with unsaturated groups according to claim 2, characterized in that: In step S3, the CO2 inlet pressure is adjusted to maintain the inlet pressure of the microchannel reactor at 0.2–0.5 MPa. In step S3, when adding the mixture of unsaturated anhydride and catalyst, the temperature of the microchannel reactor is controlled to be 80-110℃, the single-pass time through the microchannel reactor is 2-8 min, and the total reaction residence time in the microchannel is 30-60 min.

11. The method for continuous production of low molecular weight bipolar polyphenylene ethers capped with unsaturated groups according to claim 2, characterized in that: In step S3, the residual acid anhydride in the raw material and the residual hydroxyl group in the polyphenylene ether product are detected online by detector 2 (8) until the detection is qualified. The judgment index for qualified detection is: residual phenolic hydroxyl group in polyphenylene ether product <300ppm; In step S3, NH3 gas is introduced to control the pH of the reaction system to 7.0±0.2; pure water is added, and the mass ratio of pure water to 2,6-dimethylphenol in the initial reaction system is 0.5 to 1.2:

1.

12. The method for continuous production of low molecular weight bipolar polyphenylene ethers with unsaturated group-terminated capping according to claim 2, characterized in that: In step S3, the online inspection by detector 3 (10) is qualified, which means that the catalyst, metal ion and inorganic salt ion residues are monitored online. The judgment index is: catalyst residue < 5000 ppm, metal ion residue < 200 ppm, chloride ion residue < 100 ppm, methacrylic acid and acid anhydride total ion < 300 ppm. In step S3, the number average molecular weight of the low molecular weight dual-terminated polyphenylene ether product is in the range of 750 to 3500.

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